Refactoring: Introduce HTMLImport interface to form import tree.

Source/core/html/HTMLImport.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 11 matching lines @@
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
-#include "core/loader/UniqueIdentifier.h"
+#include "core/html/HTMLImport.h"
+
+#include "core/html/HTMLImportsController.h"
 
 namespace WebCore {
 
-static unsigned long s_uniqueIdentifier = 0;
-
-unsigned long createUniqueIdentifier()
+bool HTMLImport::haveChildrenLoaded()
 {
-    return ++s_uniqueIdentifier;
+    if (HTMLImportsController* controller = this->controller())
+        return controller->haveChildrenLoaded(this);
+    return true;
 }
 
 } // namespace WebCore
-